As a gas turbine engine carries out high-speed revolution under high temperatures, its components are required to have excellent performance in abrasion resistance, heat resistance and/or high-temperature corrosion resistance. Sites required to have such performance are limited in these components and also limited in surfaces thereof. Therefore, it is often executed to have proper materials such as ceramics formed as coatings on base members. As methods applicable thereto, PVD, CVD and thermal spraying can be exemplified, however, these methods may raise some technical problems in which some selected materials make it difficult to apply these methods, require very long time for processing, and require additional process steps such as masking of peripheries of subject sites so as to localize the coatings in the sites.
An art which uses discharge between an electrode and a workpiece to form a coating is disclosed in Japan Patent Application Laid-open No. H8-300227, A problem of this art is to often form a porous coating on any occasions depending on kinds of ceramics and/or operation conditions. As a porous coating is poor in bonding force among particles, it may be hard to ensure sufficient strength for the coating.